The present invention relates to an improved vibration attenuation and noise attenuation construction for a reciprocating mass, pneumatically driven tool.
Nilsson, et al, in U.S. Pat. No. 4,088,062, discloses a fluid pressure operated impact mechanism which includes a reciprocating work member cooperative with an O-ring seal to thereby define a chamber. Pressurizing fluid is admitted to the chamber causing the chamber to expand and break the seal thereby transporting the impact member.
Nilsson, et al, in U.S. Pat. No. 4,117,764, discloses an improvement over the mechanism of U.S. Pat. No. 4,088,062. The Nilsson '764 patent discloses a two mass balanced system wherein vibration is attenuated in an impact tool by maintaining opposed axially movable members, one of which is a working member and the second of which is a balancing member. A similar structure is shown in British Pat. No. 431,317.
The Nilsson, et al U.S. Pat. No. 4,117,764 further discloses that the working member and balancing member are separated by an O-ring to thereby define a chamber between the members. The O-ring seals the members and is expandable once pressurized fluid is admitted to the chamber between the two members. Expansion of the chamber beyond a predetermined limit breaks the O-ring seal and causes fluid within the chamber to exhaust. Subsequently, the members reform the chamber in combination with the O-ring. The described device provides good vibration attenuation characteristics.
The present invention constitutes an improvement over the device shown in the Nilsson '764 patent. Among the improved features of the present invention is the elimination of parts, the capability of longer life, an arrangement which will permit frequency adjustment and fine tuning of the vibration characteristics of the device, and lower cost associated with the manufacture of the device.